Angiotensin metabolism in renal proximal tubules, urine, and serum of sheep: evidence for ACE2-dependent processing of angiotensin II

Despite the evidence that angiotensin-converting enzyme (ACE)2 is a component of the renin-angiotensin system (RAS), the influence of ACE2 on angiotensin metabolism within the kidney is not well known, particularly in experimental models other than rats or mice. Therefore, we investigated the metabolism of the angiotensins in isolated proximal tubules, urine, and serum from sheep. Radiolabeled [(125)I]ANG I was hydrolyzed primarily to ANG II and ANG-(1-7) by ACE and neprilysin, respectively, in sheep proximal tubules. The ACE2 product ANG-(1-9) from ANG I was not detected in the absence or presence of ACE and neprilysin inhibition. In contrast, the proximal tubules contained robust ACE2 activity that converted ANG II to ANG-(1-7). Immunoblots utilizing an NH(2) terminal-directed ACE2 antibody revealed a single 120-kDa band in proximal tubule membranes. ANG-(1-7) was not a stable product in the tubule preparation and was rapidly hydrolyzed to ANG-(1-5) and ANG-(1-4) by ACE and neprilysin, respectively. Comparison of activities in the proximal tubules with nonsaturating concentrations of substrate revealed equivalent activities for ACE (ANG I to ANG II: 248 +/- 17 fmol x mg(-1) x min(-1)) and ACE2 [ANG II to ANG-(1-7): 253 +/- 11 fmol x mg(-1) x min(-1)], but lower neprilysin activity [ANG II to ANG-(1-4): 119 +/- 24 fmol x mg(-1) x min(-1); P < 0.05 vs. ACE or ACE2]. Urinary metabolism of ANG I and ANG II was similar to the proximal tubules; soluble ACE2 activity was also detectable in sheep serum. In conclusion, sheep tissues contain abundant ACE2 activity that converts ANG II to ANG-(1-7) but does not participate in the processing of ANG I into ANG-(1-9).

Effect of angiotensin II blockade on a new congenic model of hypertension derived from transgenic Ren-2 rats

The generation of the Lew.Tg(mRen2) congenic hypertensive rat strain, developed through a backcross of the hypertensive (mRen2)27 transgenic rat with normotensive Lewis rats, provides a new model by which primary hypertension can be studied without the genetic variability found in the original strain. The purpose of this study was to characterize the Lew.Tg(mRen2) rats by dually investigating the effects of type 1 angiotensin II (ANG II) receptor (AT(1)) blockade and angiotensin-converting enzyme (ACE) activity inhibition on the ANG-(1-7)/ACE2 axis of the renin-angiotensin system in this new hypertensive model. The control of blood pressure elicited by 12-day administration of either lisinopril (mean difference change = 92 +/- 2, P < 0.05) or losartan (mean difference change = 69 +/- 2, P < 0.05) was associated with 54% and 33% increases in cardiac ACE2 mRNA and 54% and 43% increases in cardiac ACE mRNA, respectively. Lisinopril induced a 3.1-fold (P < 0.05) increase in renal cortical expression of ACE2, whereas losartan increased ACE2 mRNA 3.5-fold (P < 0.05). Both treatment regimens increased renal ACE mRNA 2.6-fold (P < 0.05). The two therapies augmented ACE2 protein activity, as well as increased cardiac and renal AT(1) receptor mRNAs. ACE inhibition reduced plasma ANG II levels (81%, P < 0.05) and increased plasma ANG-(1-7) (265%, P < 0.05), whereas losartan had no effect on the peptides. In contrast with what had been shown in normotensive rats, ACE inhibition decreased renal ANG II excretion and transiently decreased ANG-(1-7) excretion, whereas losartan treatment was associated with a consistent decrease in ANG-(1-7) urinary excretion rates. In response to the treatments, the expression of both renal cortical renin and angiotensinogen mRNAs was significantly augmented. The paradoxical effects of blockade of ANG II synthesis and activity on urinary excretion rates of the peptides and plasma angiotensins levels suggest that, in Lew.Tg(mRen2) congenic rats, a failure of compensatory ACE2 and ANG-(1-7)-dependent vasodepressor mechanisms may contribute both to the development and progression of hypertension driven by increased formation of endogenous ANG II.

Enhanced expression of Ang-(1-7) during pregnancy

Pregnancy is a physiological condition characterized by a progressive increase of the different components of the renin-angiotensin system (RAS). The physiological consequences of the stimulated RAS in normal pregnancy are incompletely understood, and even less understood is the question of how this system may be altered and contribute to the hypertensive disorders of pregnancy. Findings from our group have provided novel insights into how the RAS may contribute to the physiological condition of pregnancy by showing that pregnancy increases the expression of both the vasodilator heptapeptide of the RAS, angiotensin-(1-7) [Ang-(1-7)], and of a newly cloned angiotensin converting enzyme (ACE) homolog, ACE2, that shows high catalytic efficiency for Ang II metabolism to Ang-(1-7). The discovery of ACE2 adds a new dimension to the complexity of the RAS by providing a new arm that may counter-regulate the activity of the vasoconstrictor component, while amplifying the vasodilator component. The studies reviewed in this article demonstrate that Ang-(1-7) increases in plasma and urine of normal pregnant women. In preeclamptic subjects we showed that plasma Ang-(1-7) was suppressed as compared to the levels found in normal pregnancy. In addition, kidney and urinary levels of Ang-(1-7) were increased in pregnant rats coinciding with the enhanced detection and expression of ACE2. These findings support the concept that in normal pregnancy enhanced ACE2 may counteract the elevation in tissue and circulating Ang II by increasing the rate of conversion to Ang-(1-7). These findings provide a basis for the physiological role of Ang-(1-7) and ACE2 during pregnancy.

Vasopeptidase inhibition and Ang-(1-7) in the spontaneously hypertensive rat

BACKGROUND

Omapatrilat, a new vasopeptidase inhibitor, inhibits the activity of angiotensin-converting enzyme (ACE) and neutral endopeptidase 24.11 (NEP). Because these two enzymes participate in the degradation of the vasodilator and natriuretic peptide, angiotensin-(1-7) [Ang-(1-7)], we assessed whether omapatrilat treatment is associated with changes in the plasma and urinary excretion rates of the angiotensins.

METHODS

We investigated in spontaneously hypertensive rats (SHR) (0.24 kg body weight) the effect of omapatrilat on plasma and urinary concentrations of angiotensin (Ang) I, Ang II and Ang-(1-7) during 17 days of administration of either the drug (N = 15, 100 micromol/kg/day) or vehicle (N = 14) in the drinking water. Hemodynamic and renal excretory function studies were associated with histological examination of the expression of Ang-(1-7) in the kidneys of both vehicle and omapatrilat-treated SHRs.

RESULTS

Omapatrilat induced a sustained lowering of systolic blood pressure (-68 mm Hg) without changes in cardiac rate. The mild positive water balance produced by omapatrilat did not cause natriuresis or kaliuresis, although it was associated with a significant decrease in urine osmolality. Blood pressure normalization was accompanied by increases in plasma Ang I (2969%), Ang II (57%), and Ang-(1-7) (163%) levels, paralleling pronounced increases in urinary excretion rates of Ang I and Ang-(1-7) but not Ang II. Detection of Ang-(1-7) immunostaining in the kidneys of five other SHR exposed either to vehicle (N = 3) or omapatrilat (N = 2) ascertained the source of the Ang-(1-7) found in the urine. Intense Ang-(1-7) staining, more pronounced in omapatrilat-treated SHR, was found in renal proximal tubules throughout the outer and inner regions of the renal cortex and the thick ascending loop of Henle, whereas no Ang-(1-7)-positive immunostaining was found in glomeruli and distal tubules.

CONCLUSIONS

Omapatrilat antihypertensive effects caused significant activation of the renin-angiotensin system associated with increases in urinary excretion rates of Ang I and Ang-(1-7). Combined studies of Ang-(1-7) metabolism in urine and immunohistochemical studies in the kidney revealed the existence of an intrarenal source, which may account for the pronounced increase in the excretion rate of the vasodilator heptapeptide. These findings provide further evidence for a contribution of Ang-(1-7) to the regulation of renal function and blood pressure.

Urinary vasodilator and vasoconstrictor angiotensins during menstrual cycle, pregnancy, and lactation

Since normal human pregnancy is characterized by normotension in the face of an increased renin-angiotensin-aldosterone system (RAAS), we evaluated the temporal pattern of urinary excretion of a novel vasodilator within this system, angiotensin-(1-7) (Ang-[1-7]), during the menstrual cycle, pregnancy, and lactation. The urinary profiles of Ang I, Ang II, human chorionic gonadotropin, 17beta-estradiol, and progesterone were also determined. During the menstrual cycle, urinary Ang-(1-7) and Ang II remained stable (mean cycle value: 94.6 +/- 11.3 and 11.4 +/- 1.1 pmol/g of creatinine, respectively) in nine females. In 10 normal pregnant women, urinary Ang-(1-7) and Ang II increased throughout gestation, averaging 1499.8 +/- 310 and 224.4 +/- 58 pmol/g of creatinine, respectively (p < 0.05) at wk 35 and falling during lactation to 394.0 +/- 95 and 65.7 +/- 20 pmol/ g of creatinine (p < 0.05), respectively. The Ang-(1-7)/Ang II ratio was unchanged in the different reproductive periods. During the menstrual cycle, Ang II and Ang-(1-7) correlated with 17beta-estradiol and progesterone using multivariate analysis (r = 0.31, p < 0.001) and r = 0.28, p < 0.02, respectively). During gestation, 17beta-estradiol and progesterone correlated with urinary Ang-(1-7) (r = 0.48, p < 0.001 and r = 0.47, p < 0.001, respectively) and Ang II (r = 0.24, p < 0.03 and r = 0.25, p < 0.03, respectively); by multiple regression, only Ang-(1-7) correlated with both steroids (r = 0.49,p < 0.001). The progressive rise of Ang-(1-7) throughout gestation, probably modulated by estrogen and progesterone, suggests a physiologic counterregulation within the RAAS.

Pregnancy enhances the angiotensin (Ang)-(1-7) vasodilator response in mesenteric arteries and increases the renal concentration and urinary excretion of Ang-(1-7)

The vasoactive effect of angiotensin (Ang)-(1-7) in mesenteric resistance arteries together with its plasma and kidney concentration and urinary excretion was assessed in pregnant and virgin rats. Mesenteric arteries (230-290 microm) were mounted in a pressurized myograph system and Ang-(1-7) concentration-dependent response curves (10(-10)-10(-5) M) were determined in arteries preconstricted with endothelin-1 (10(-7) M). The Ang-(1-7) response was investigated in vessels with and without pretreatment with the Ang-(1-7) antagonist [D-[Ala(7)]-Ang-(1-7)] (10(-7) M). Ang-(1-7) caused a significantly enhanced, concentration-dependent dilation of mesenteric vessels (EC(50) = 2.7 nM) from pregnant compared with virgin female rats. D-[Ala(7)]-Ang-(1-7) eliminated the vasodilator effect of Ang-(1-7). There was no significant change in plasma concentration of Ang-(1-7) in pregnant animals. On the other hand, 24 h urinary excretion and kidney concentration of Ang-(1-7) were significantly higher in pregnant animals. The increased mesenteric dilation to Ang-(1-7) with enhanced kidney concentration and 24 h urinary excretion rate of Ang-(1-7) suggests an important role for this peptide in cardiovascular regulation during pregnancy.

Differential response of angiotensin peptides in the urine of hypertensive animals

Urinary excretion rates of angiotensin I (Ang I), angiotensin II (Ang II), and angiotensin-(1-7) [Ang-(1-7)] were determined in normotensive Sprague Dawley (SD), spontaneously hypertensive (SHR), and mRen-2 transgenic hypertensive animals before and following blockade of Ang II synthesis or activity for two weeks. This study was performed to determine for the first time whether inhibition of Ang II alters the excretion of angiotensin peptides in the urine. Rats were given either tap water or water medicated with lisinopril, losartan or both agents in combination. Blood pressure was monitored at regular intervals during the experiment by the tail-cuff method, and once again at the end of the study with a catheter implant into a carotid artery. Metabolic studies and 24 h urinary excretion variables and angiotensin peptides were determined before and during the procedures. While all three treatments normalized the blood pressure of hypertensive animals, therapy with either lisinopril or the combination of lisinopril and losartan had a greater antihypertensive effect in both SHR and [mRen-2]27 transgenic hypertensive rats. In the urine, the concentration of the angiotensins (normalized by 24-h creatinine excretion) was several-fold higher in the untreated hypertensive animals than in normotensive SD rats. In SD rats, lisinopril or lisinopril and losartan produced a sustained rise in urinary levels of Ang-(1-7) without changes in the excretion of Ang I and Ang II. In contrast, Ang I and Ang-(1-7) were significantly elevated in SHR medicated with lisinopril alone or in combination with losartan. Only losartan, however, augmented urinary levels of Ang II in the SHR. The antihypertensive effects of the three separate regimens had no effect on the urinary excretion of angiotensin peptides in [mRen-2]27 transgenic hypertensive rats. These data show that Ang I and Ang-(1-7) are excreted in large amounts in the urine of SD, SHR and [mRen-2]27 hypertensive rats. The unchanged Ang-(1-7) excretion in transgenic hypertensive (Tg+) rats after inhibition of the renin-angiotensin system agrees with the previous finding of a reduced plasma clearance of the peptide in this model of hypertension. The data suggest that this form of hypertension may be associated with increased activity of an endogenous converting enzyme inhibitor.

Urinary excretion of angiotensin I, II, arginine vasopressin and oxytocin in patients with anaphylactoid reactions

Human urine samples, purified on octadecasilyl-silica cartridges, contained immunoreactive angiotensin I, II, arginine vasopressin and oxytocin. The daily excretion of these peptides in healthy volunteers was 190.00 +/- 38.43 (n = 12), 17.48 +/- 3.09 (n = 12), 63.43 +/- 14.84 (n = 8) and 13.52 +/- 1.42 (n = 7) pmol/24 hr, respectively (mean +/- s.e.m.). Patients with a history of anaphylactoid reactions to drugs or food additives showed clinical symptoms such as urticaria, flush, nausea, dizziness and hypotension after oral provocation with cyanocobalamine, propyphenazone, acetylsalicylic acid and sodium benzoate. In five of the seven patients, angiotensin I and II were increased several fold in the urine fractions after symptoms were reported. The average increase in the urine concentration of both peptides was fourfold and 5.5-fold. In three out of five patients, the mean excretion of arginine vasopressin and oxytocin immunoreactive material was also elevated by a factor of 5.7 and 4.4, respectively. Oral provocation with a placebo failed to elicit anaphylactoid symptoms or an increase in the urine levels of angiotensin I or angiotensin II. Angiotensin I and angiotensin II-like immunoreactivity could be characterized on HPLC as Ile5-angiotensin I, Ile5-angiotensin II and angiotensin II metabolites. HPLC characterization of immunoreactive arginine vasopressin and oxytocin in two different gradient systems showed retention times different than the retention times of the corresponding synthetic standard peptides indicating that both peptides are not authentic AVP and OXT. These results suggest that angiotensin I and angiotensin II may be involved in the clinical events observed during some forms of anaphylactoid reactions.

The effect of intravenous frusemide on urine dopamine in normal volunteers: studies with indomethacin and carbidopa

1. The urine dopamine response to intravenous frusemide (30 mg) was investigated in 15 salt replete male volunteers. The effects of oral indomethacin (100 mg) and oral carbidopa (100 mg) given before intravenous frusemide were studied in the same group of subjects. 2. Frusemide produced a significant increase in urine dopamine output within 15 min. 3. Indomethacin attenuated the natriuretic and renin responses to frusemide, but did not alter urine dopamine output. 4. Carbidopa lowered urine dopamine to undetectable levels, but did not significantly affect the natriuretic and renin responses to frusemide. 5. We conclude that urine dopamine excretion after frusemide is not directly related to increased sodium excretion or renin response and it is not mediated by the prostaglandins. In addition, dopamine does not contribute to the renal actions of frusemide under normal conditions.

The origin of urinary angiotensins in humans

To examine whether urinary angiotensin (ANG) I and II excretion responds to changes in plasma ANG I and ANG II, ANG I or ANG II was infused in seven healthy subjects pretreated with a 340-mmol sodium diet and 20 mg of enalapril twice daily. Infusion rates were 4, 8, 16, and 32 pmol/kg per minute for ANG I and 1, 4, and 8 pmol/kg per minute for ANG II. Baseline ANG I and ANG II excretions averaged 10 and 20 fmol/min, respectively, which is approximately 0.3 and 5% of the filtered loads. Despite a 20-fold increase in plasma ANG I during ANG I infusion, urinary ANG I did not increase. Similarly, the 30-fold increase in plasma ANG II during ANG II infusion was not followed by an increase in ANG II excretion, but in fact by a decrease in urinary ANG I and ANG II. In a separate study, urinary ANG I and ANG II were measured before and after the oral administration of 20 mg of enalapril in eight healthy volunteers taking 400, 200, or 20 mmol of NaCl daily. In contrast to the considerable effects on plasma ANG I and ANG II and renal hemodynamics, enalapril had no effect on urinary ANG I and ANG II. Variation of sodium intake had predictable effects on plasma ANG I and ANG II but did not affect urinary ANG I and ANG II. These data suggest that urinary ANG I and ANG II originate from an intrarenal source. The independency of sodium intake and ANG-converting enzyme make the juxtaglomerular apparatus as the site responsible for the production of this ANG unlikely.

Increased urinary excretion of angiotensin during anaphylactoid reactions

Immunoreactive angiotensin I (ANG I) and angiotensin II (ANG II) were measured in human urine, after purification on octadecasilyl-silica cartridges. The total daily excretion of ANG I and II in healthy volunteers was 292.2 +/- 62.5 and 12.2 +/- 2.5 pmol/24 h (mean +/- SEM; n = 14). No differences in the concentrations of ANG I or II were detected between females and males. Although lower levels of ANG I and II were found during the nighttime, no clear-cut circadian rhythm in the excretion of the peptides was found. ANG II was not degraded in acidified urine which shows the effective inhibition of ANG-II-degrading enzymes. Oral provocation tests (OPT) in patients with a history of anaphylactoid reactions (AR) to drugs, foods and food additives were associated with elevated ANG I and II concentrations when symptoms of anaphylaxis occurred. The excretion of ANG I increased by a factor of 7.8 +/- 2.4 and the excretion of ANG II by a factor of 6.1 +/- 1.6 (mean +/- SEM; n = 15). In patients with negative OPT and no clinical symptoms of anaphylaxis, the levels of ANG I and II remained unchanged (n = 26). It is concluded that angiotensin peptides play a role during the events of AR. The peptides may be considered as counteracting factors which stabilize cardiovascular functions.

Evidence for a role of angiotensin converting enzyme 2 in proteinuria of idiopathic nephrotic syndrome

Introduction: Renin angiotensin system (RAS) plays a role in idiopathic nephrotic syndrome (INS). Most studies investigated only the classical RAS axis. Therefore, the aims of the present study were to evaluate urinary levels of RAS molecules related to classical and to counter-regulatory axes in pediatric patients with INS, to compare the measurements with levels in healthy controls and to search for associations with inflammatory molecules, proteinuria and disease treatment. Subjects and methods: This cross-sectional study included 31 patients with INS and 19 healthy controls, matched for age and sex. Patients and controls were submitted to urine collection for measurement of RAS molecules [Ang II, Ang-(1-7), ACE and ACE2] by enzyme immunoassay and cytokines by Cytometric Bead Array. Findings in INS patients were compared according to proteinuria: absent (<150 mg/dl, n = 15) and present (≥150 mg/dl, n = 16). Results: In comparison to controls, INS patients had increased Ang II, Ang-(1-7) and ACE, levels while ACE2 was reduced. INS patients with proteinuria had lower levels of ACE2 than those without proteinuria. ACE2 levels were negatively correlated with 24-h-proteinuria. Urinary concentrations of MCP-1/CCL2 were significantly higher in INS patients, positively correlated with Ang II and negatively with Ang-(1-7). ACE2 concentrations were negatively correlated with IP-10/CXCL-10 levels, which, in turn, were positively correlated with 24-h-proteinuria. Conclusion: INS patients exhibited changes in RAS molecules and in chemokines. Proteinuria was associated with low levels of ACE2 and high levels of inflammatory molecules.

The protective arm of the renin-angiotensin system may counteract the intense inflammatory process in fetuses with posterior urethral valves

OBJECTIVE

Posterior urethral valve is the most common lower urinary tract obstruction in male children. A high percentage of patients with posterior urethral valve evolve to end-stage renal disease. Previous studies showed that cytokines, chemokines, and components of the renin-angiotensin system contribute to the renal damage in obstructive uropathies. The authors recently found that urine samples from fetuses with posterior urethral valve have increased levels of inflammatory molecules. The aim of this study was to measure renin-angiotensin system molecules and to investigate their correlation with previously detected inflammatory markers in the same urine samples of fetuses with posterior urethral valve.

METHODS

Urine samples from 24 fetuses with posterior urethral valve were collected and compared to those from 22 healthy male newborns at the same gestational age (controls). Renin-angiotensin system components levels were measured by enzyme-linked immunosorbent assay.

RESULTS

Fetuses with posterior urethral valve presented increased urinary levels of angiotensin (Ang) I, Ang-(1-7) and angiotensin-converting enzyme 2 in comparison with controls. ACE levels were significantly reduced and Ang II levels were similar in fetuses with posterior urethral valve in comparison with controls.

CONCLUSIONS

Increased urinary levels of angiotensin-converting enzyme 2 and of Ang-(1-7) in fetuses with posterior urethral valve could represent a regulatory response to the intense inflammatory process triggered by posterior urethral valve.

Response of urinary angiotensin to challenges of the renin-angiotensin system

Angiotensin has an intrarenal action which may not parallel its action in the general circulation. We investigated whether the urinary excretion rates of angiotensin I and II (UV-AI, UV-AII) can be used as a marker of renal production. We therefore measured UV-AI, UV-AII, plasma angiotensin I and II (PAI, PAII), and plasma renin activity (PRA) in healthy subjects under conditions influencing the renin-angiotensin system: captopril injection (n = 7), enalapril treatment (n = 9), furosemide infusion on high and low sodium intake (n = 6), indomethacin treatment (n = 8), and head-out water immersion (three sodium intakes). After captopril (acute) and enalapril (chronic), PAI and PRA increased, PAII decreased, but neither UV-AI nor UV-AII changed. During furosemide infusion, PAI, PAII, PRA, as well as UV-AI and UV-AII increased. During indomethacin treatment, PAI, PAII, and PRA decreased, whereas UV-AI and UV-AII did not change consistently. Sodium restriction increased PAI, PAII, and PRA, but did not alter UV-AI and UV-AII. Head-out immersion decreased PAI, PAII, and PRA, but did not change UV-AI and UV-AII. The relative constancy of the urinary AI and AII excretion rates makes it doubtful whether urinary angiotensins reflect changes of renal angiotensin production.

A reliable radiometric assay for the determination of angiotensin I-converting enzyme activity in urine

We present a radiometric assay for the determination of urinary angiotensin-converting enzyme activity, using benzoyl-[1-14C]glycyl-L-histidyl-L-leucine as the substrate. An optimal pH of 8.3, an optimal chloride concentration of 0.375 mol/l and complete inhibition by EDTA-Na2, captopril and enalaprilat confirm the specificity of the assay. Comparison of dialysis and ultrafiltration for concentration of urine showed the existence of angiotensin-converting enzyme inhibitors in human urine. Dialysis against water was the more effective method for avoiding enzyme inhibition. After dialysis of urine, the assay was linear with time and with enzyme concentration; it was highly sensitive (60 mU/l) and showed good reproducibility. Under our technical conditions, we found angiotensin-converting enzyme activity in urine samples with quantitatively abnormal protein contents, but not in normal urine. Urinary angiotensin-converting enzyme did not correlate with proteinuria nor with water-salt parameters or creatinine. We confirm the kidney tubular epithelial origin of the enzyme, and propose the use of our assay to study urinary angiotensin-converting enzyme as a marker of renal tubular damage.

Urinary angiotensin excretion during sodium restriction and diuretics

The urinary excretion rate and plasma concentration of angiotensin I (UAI, PAI) and angiotensin II (UAII, PAII), and plasma renin activity (PRA) were measured in seven healthy volunteers in the supine and upright position both on free and restricted sodium intakes. The same variables were measured before and after intravenous injection of furosemide, as well as before and during intravenous infusion of chlorothiazide. Assumption of the upright posture as well as sodium restriction increased PAI, PAII, and PRA, but UAI and UAII excretion were not altered by these manoeuvres. Furosemide injection resulted in increases of all variables, albeit that PAI and PAII were elevated to a lesser extent then PRA. Chlorothiazide infusion caused a reduction in PAI, PAII, and PRA, whereas UAI and UAII excretion increased modestly. The discrepancies between changes in plasma and urinary AI and AII may indicate that urinary angiotensin excretion provides information which is supplementary to that of plasma angiotensins.

[Urinary levels of angiotensin-(1-7) and angiotensin II in patients with severe aortic stenosis]

OBJECTIVE

Strengthen knowledge about the pathophysiology of aortic stenosis.

METHODS

Urinary levels of angiotensin-(1-7) and angiotensin II were compared between two samples: A) forty five patients with severe aortic stenosis, without systemic arterial hypertension and with normal kidney and normal left ventricular systolic function; B) control group: twenty one persons without cardiovascular disease.

NULL HYPOTHESIS

there would be no difference between urinary levels.

RESULTS

The average of angiotensin-(1-7) urinary concentration in severe aortic stenosis patients was 2.102 pmol/mL and 5.591 pmol/mL for the control group. The average of Ang II was 0.704 pmol/mL and 0.185 pmol/mL respectively. Using t-Student test, we determine that the difference in urinary concentration of angiotensin-(1-7) [p=0.633] and the difference of angiotensin II (p=0.631), were statistically significant.

CONCLUSION

documented a statistically significant difference in urinary levels angiotensin II and angiotensin-(1-7) within the group of patients with severe aortic stenosis.

Presence of angiotensin peptides in human urine

Immunoreactive angiotensin I and angiotensin II were found in human urine that was purified on octadecasilylsilica cartridges. The daily excretion of angiotensin I and II in healthy volunteers was 189.00 (SE 38.36) and 17.54 (SE 3.07) pmol/24 h or 148.09 (SE 32.22) and 12.82 (SE 2.34) pmol/L, respectively (n = 12). No circadian rhythm was observed in the excretion patterns of angiotensin I and II. In vitro degradation of angiotensin I or II could not be detected in acidified urine samples. A marked increase in the excretion of angiotensin I and II could be demonstrated in patients with anaphylactoid reactions to drugs and food additives after oral challenge. Immunoreactive angiotensin I and II could be characterized by HPLC as Ile5-angiotensin I, Ile5-angiotensin II, and angiotensin II metabolites.